484 Modern Food Microbiology
and thus have no sanitary significance when found in foods. Mundt
59 studied E. faecalis from humans,
plants, and other sources and found that the nonfecal indicators could be distinguished from the
more fecal types by their reaction in litmus milk and their fermentation reactions in melizitose and
melibiose broths. In another study of 2,334 isolates of E. faecalis from dried and frozen foods, a high
percentage of strains bore a close similarity to the vegetation-resident types and, therefore, were not
of any sanitary significance.
57 When used as indicators of sanitary quality in foods, it is necessary
to ascertain whether E. faecalis isolates are of the vegetation type or whether they represent those of
human origin. Enterococci may also be found in dust. They are rather widely distributed, especially
in such places as slaughterhouses and curing rooms, where pork products are handled.
With respect to the use of the classic enterococci as indicators of water pollution, some investigators
who have studied their persistence in water have found that they die off at a faster rate than coliforms,
whereas others found the opposite. Leininger and McCleskey
48 noted that enterococci do not multiply
in water as coliforms sometimes do. Their more exacting growth requirements may be taken to indicate
a less competitive role in water environments. In sewage, coliforms and the classic enterococci were
found to exist in high numbers, but approximately 13 times more coliforms than enterococci were
found.
50
In a study conducted when the genus Enterococcus consisted of only eight species, Devriese et al.
20
studied 264 isolates of enterococci obtained from farm animal intestines. Strains were selected solely
on the basis of their growth in 40% bile and 6.5% NaCl. Of the 264 isolates, 255 conformed to one
of the 8 species, with E. faecalis, E. faecium, and E. hirae, representing 37.6%, 29.8%, and 23% of
the isolates, respectively. Other species found were E. durans (5.1%), E. gallinarum (1.6%), E. avium
(1.2%), E. mundtii (1.2%), and E. casseliflavus (<1%). These 255 isolates were obtained from eight
animal species, with poultry, cattle, and pigs yielding the largest number of isolates.
In a later study of enterococci in foods of animal origin,
19 a total of 161 strains were isolated from the
following foods in Belgium: meats,
84 cheeses,
54 fish and shellfish,
42 and cheese–meat combinations.
30
E. faecium accounted for 58.4% (94 of 161) and E. faecalis for 26.1% (42 of 161) of the isolates with
9.3% (15 of 161) being represented by E. hirae/E. durans. None of the last 10 or so species to be
named was identified in either of the above studies.
Relationship to Sanitary Quality of Foods
In this section, the enterococci discussed are those that were defined prior to 1984. A large number of
investigators found the classic enterococci to be better than coliforms as indicators of food sanitary
quality, especially for frozen foods. In one study, enterococcal numbers were more closely related to
aerobic plate counts (APC) than to coliform counts, whereas coliforms were more closely related to
enterococci than to APC.
30 Enterococci have been found in greater numbers than coliforms in frozen
foods (Table 20–6). In a study of 376 samples of commercially frozen vegetables, Burton
9 found
that coliforms were more efficient indicators of sanitation than enterococci prior to freezing, whereas
enterococci were superior indicators after freezing and storage. In samples stored at −20
◦ C for 1–3
months, 81% of enterococci and 75% of coliforms survived. After 1 year, 89% of enterococci survived
but only 60% of coliforms. In another study, enterococci remained relatively constant for 400 days
when stored at freezing temperatures. Enterococci were recovered from 57% of 14 samples of dried
foods, whereas 87% of 13 different frozen vegetables yielded these organisms, many of which were
of the vegetation-resident types.
57 The relative longevity of coliforms and enterococci in frozen fish
sticks is presented in Table 20–7.
Overall, the elevation of the once “fecal strep” to the status of a genus and the expansion of
the genus to include some species that appear to have no natural association with fecal matter raise
and thus have no sanitary significance when found in foods. Mundt
59 studied E. faecalis from humans,
plants, and other sources and found that the nonfecal indicators could be distinguished from the
more fecal types by their reaction in litmus milk and their fermentation reactions in melizitose and
melibiose broths. In another study of 2,334 isolates of E. faecalis from dried and frozen foods, a high
percentage of strains bore a close similarity to the vegetation-resident types and, therefore, were not
of any sanitary significance.
57 When used as indicators of sanitary quality in foods, it is necessary
to ascertain whether E. faecalis isolates are of the vegetation type or whether they represent those of
human origin. Enterococci may also be found in dust. They are rather widely distributed, especially
in such places as slaughterhouses and curing rooms, where pork products are handled.
With respect to the use of the classic enterococci as indicators of water pollution, some investigators
who have studied their persistence in water have found that they die off at a faster rate than coliforms,
whereas others found the opposite. Leininger and McCleskey
48 noted that enterococci do not multiply
in water as coliforms sometimes do. Their more exacting growth requirements may be taken to indicate
a less competitive role in water environments. In sewage, coliforms and the classic enterococci were
found to exist in high numbers, but approximately 13 times more coliforms than enterococci were
found.
50
In a study conducted when the genus Enterococcus consisted of only eight species, Devriese et al.
20
studied 264 isolates of enterococci obtained from farm animal intestines. Strains were selected solely
on the basis of their growth in 40% bile and 6.5% NaCl. Of the 264 isolates, 255 conformed to one
of the 8 species, with E. faecalis, E. faecium, and E. hirae, representing 37.6%, 29.8%, and 23% of
the isolates, respectively. Other species found were E. durans (5.1%), E. gallinarum (1.6%), E. avium
(1.2%), E. mundtii (1.2%), and E. casseliflavus (<1%). These 255 isolates were obtained from eight
animal species, with poultry, cattle, and pigs yielding the largest number of isolates.
In a later study of enterococci in foods of animal origin,
19 a total of 161 strains were isolated from the
following foods in Belgium: meats,
84 cheeses,
54 fish and shellfish,
42 and cheese–meat combinations.
30
E. faecium accounted for 58.4% (94 of 161) and E. faecalis for 26.1% (42 of 161) of the isolates with
9.3% (15 of 161) being represented by E. hirae/E. durans. None of the last 10 or so species to be
named was identified in either of the above studies.
Relationship to Sanitary Quality of Foods
In this section, the enterococci discussed are those that were defined prior to 1984. A large number of
investigators found the classic enterococci to be better than coliforms as indicators of food sanitary
quality, especially for frozen foods. In one study, enterococcal numbers were more closely related to
aerobic plate counts (APC) than to coliform counts, whereas coliforms were more closely related to
enterococci than to APC.
30 Enterococci have been found in greater numbers than coliforms in frozen
foods (Table 20–6). In a study of 376 samples of commercially frozen vegetables, Burton
9 found
that coliforms were more efficient indicators of sanitation than enterococci prior to freezing, whereas
enterococci were superior indicators after freezing and storage. In samples stored at −20
◦ C for 1–3
months, 81% of enterococci and 75% of coliforms survived. After 1 year, 89% of enterococci survived
but only 60% of coliforms. In another study, enterococci remained relatively constant for 400 days
when stored at freezing temperatures. Enterococci were recovered from 57% of 14 samples of dried
foods, whereas 87% of 13 different frozen vegetables yielded these organisms, many of which were
of the vegetation-resident types.
57 The relative longevity of coliforms and enterococci in frozen fish
sticks is presented in Table 20–7.
Overall, the elevation of the once “fecal strep” to the status of a genus and the expansion of
the genus to include some species that appear to have no natural association with fecal matter raise